Operating temperature and power-supply voltage affect both the life and the speed performance of integrated circuits (ICs). Elevated operating temperatures can lead to premature failure or reduced performance, for instance, degrading frequency response or increasing distortion. Unstable power-supply voltages can also lead to premature failure and reduced performance.
IC manufacturers thoroughly test their ICs prior to sale to guarantee functionality and dynamic performance under given temperature and power-supply specifications. Only ICs that pass such rigorous tests are sold to Original Equipment Manufacturers (OEMs). OEMs then include these ICs in more complex systems, which typically include collections of ICs on printed circuit boards (PCBs).
Systems that perform a particular function (e.g., signal processing) typically include different kinds of ICs mounted on one or more PCBs. Power-supply and thermal-management schemes are used during PCB layout to ensure that thermal, power and supply-voltage requirements are met for each IC.
High performance systems (e.g., telecommunication systems) built on densely populated PCBs are highly susceptible to excessive noise and overheating. The noise problem is due in part to electromagnetic coupling between closely spaced, high-speed ICs operating at different speeds and supply voltages. Ineffective or failed power-supply management schemes can exacerbate these problems—or at least fail to effectively address them—leading to power-supply problems commonly referred to as “power flickering” or “flicker effects.” Depending on its magnitude, power flickering can cause one or more ICs to fail to meet their timing or functional specifications. Similarly, a failed or ineffective thermal management scheme can cause one or more ICs to fail.
Should an OEM's system fail, the OEM may trace the failure to a manufacturer's IC and solicit the manufacturer's help in evaluating the IC and pinpointing the failure mechanism. Determining whether a performance failure is due to power flickering or excessive heat can be very challenging because active circuits in a device under test (DUT) produce both flicker and heat. For example, substantial AC activity on a DUT generates heat as current is periodically drawn from power supplies, and the periodic drawing of current produces flicker effects. Thus, to determine the cause of a performance failure, there exists a need for a means of decoupling the effects of temperature and flicker.